Yes, I had one trip with them recently. I was actually attracted to the chance to fly a Bulldog again as I learnt on the Bulldog with the UAS.
As I've only had one trip, so far, I can only speak from limited experience - but I was impressed. Very professional outfit, but not intimidating. The pilots are ex (or current) RAF and are very very experienced - and are very good at imparting that experience too. It also gives you an invaluable insight into how the some of the best flyers in the business go about their flying.
However, I would offer some advice if I may. The "advanced PPL training course" provides training on more robust handling skills (full stalls/spins/elementary aeros) and some other military techniques such as constant angle approaches. You will, in effect, be doing what you would have done if you had done your ab-initio training in the RAF. Not by any means a bad thing, but it may not coincide with you are hoping to gain from it. If you are looking for more experienced/advanced instruction of flying a Warrior/C172 from A to B you may find yourself paying a lot of money for something off-topic to some extent. Also bear in the mind the aircraft they operate are a little more sophisticated than your average trainer (e.g constant speed unit, more poke, less stable etc).
I personally would like to see a course which covers the differences between "average" PPL flying and CPL flying...e.g stricter tolerances, more IMC work, more thorough planning, handling different airspaces professionally and so on. Or in other words, a course based on Nigel Everett's book "Beyond the PPL"!
So, I would recommend Ultimate High..but be clear what it is you want out of it.
Feel free to PM me if you like....
Cheers